Pyrethroid-based insecticide products used to eliminate insect-borne diseases had come under scrutiny due to potential links to the insecticide's effects on bull reproductive health.
But Patrick Gunn, ISU Extension cow-calf specialist, and Tyler Dohlman, ISU VDPAM adjunct instructor, said in a recent Growing Beef newsletter from the University that the study in question that illustrated some links, did not indicate the amount, type, or route of pyrethroid exposure.
Thus, questions for many veterinarians and producers remain as to whether using pyrethroid-based products according to label are detrimental to fertility of the beef herd.
According to National Animal Health Monitoring System by the USDA, over half of beef operations use some type of insecticide fly control and more than 70% of larger herds (of more than 50 head) use insecticides.
A new study from Iowa State University reviewed 30 yearling Angus bulls, treated with a commercial insecticide containing 5% permethrin (synthetic Type I pyrethroid). Another 30 bulls were left untreated.
Breeding soundness exams and testosterone concentrations were assessed prior to and 14 days after treatment. Five weeks after treatment, bulls were harvested and testicular health was assessed.
Although minor differences in type of sperm abnormalities were noted, overall semen motility, morphologically normal sperm, testosterone, and testicular health were not impacted as a result of pyrethrin administration, Gunn and Dohlman said.
Thus, data from this study indicate that a single use of permethrin at label dose not affect that ability for yearling bulls to pass a standard Breeding Soundness Exam and should be considered safe for use.